The disclosure relates to a valve cartridge for an adjustable valve, and to an associated solenoid valve.
Adjustable solenoid valves are increasingly being used for controlling the braking force in hydraulic brake systems. The particular requirement of these valves as compared to the switching valves is that they have to keep the partial stroke stable over a relatively long period of time. No electrical, hydraulic or mechanical interference, which moves the valve out of the equilibrium position, must be amplified by the valve. Amplification of the interference leads to oscillations which cause a fluctuation in pressure, noise and a reduction in stability. In modern brake systems, the adjustable valve is stabilized by hydraulic damping. Movement of the valve causes fluid to be interchanged between two chambers which are separated by a connection/line. Some of the energy is converted into heat in the line due to dissipation effects, this leading to stabilization of the valve. The amount of energy discharged from the system depends on the geometry of the connection.
The effect of the hydraulic damping elements depends on the viscosity of the fluid as well as on the geometry of the connection. Since the ambient temperature changes during operation, the viscosity of the liquid also changes. Damping can therefore vary up to a factor of 1000. Furthermore, air bubbles in the liquid influence the viscosity. The damping effect can therefore fluctuate in a stochastic manner. In order to achieve a reproducible valve reaction, the armature space has to be carefully ventilated. The opposing properties of an armature space which can be easily ventilated and the desired high level of damping make it particularly difficult to design the valve with hydraulic damping elements.
Laid-open specification DE 10 2007 053 134 A1 describes a valve cartridge for a solenoid valve, and an associated solenoid valve. The described valve cartridge for a solenoid valve comprises a capsule, a magnet armature which is movably guided within the capsule, a valve insert which is inserted into the capsule by way of a first end, and a valve body having a main valve seat. A plunger is guided in a longitudinally movable manner within the valve insert, the said plunger having a closing element with a sealing element which enters the main valve seat of the valve body in a sealing manner in order to provide a sealing function. The plunger can be moved against the force of a return spring within the valve insert by the magnet armature, wherein the magnet armature is moved by a magnetic force which is generated by a magnet assembly. In order to generate a magnetic flux, the magnet assembly comprises a housing casing, a winding support, a coil winding and a covering disk and is pressed, for example, onto the capsule of the valve cartridge.